The present invention relates to analytical furnaces and particularly to an improved electrode and vacuum system for cleaning the electrodes and furnace area of a resistance furnace.
Analytical furnaces heat specimens, such as chips and pin samples, and the like, typically ranging in mass of about 1 gram or less in a crucible. Resistance furnaces employ graphite crucibles clamped between two electrodes which pass an electrical current through the crucible, heating specimens to temperatures of 2500° C. or higher. The gaseous byproducts of fusing the specimen are then swept by an inert gas through the furnace system to an analyzer for the subsequent analysis of the specimen gases of interest using suitable detectors. Such an analyzer is represented by Model TCH600 commercially available from Leco Corporation of St. Joseph, Mich.
During the heating of a specimen, the enclosed furnace chamber becomes contaminated with debris, dust, soot, and the like from the byproducts of fusing the sample and needs to be frequently cleaned. In the past, between cycles of analysis, a vacuum was supplied to the general area of the electrodes for removing such dust and debris. Also, a powered rotary brush has been employed in the furnace area of a resistance furnace to remove debris from the electrodes. Although such a system has been relatively successful, with the increased sensitivity of detectors and the ability to measure lower levels of analytes, there remains a need to more frequently clean the furnace as well as improve the cleaning of analytical furnaces between analyses.